1. Field of the Invention
This invention relates to balloon catheters which are especially useful in medical dilatation procedures.
2. Background
In "Nonoperative Dilatation of Coronary-Artery Stenosis--Percutaneous Transluminal Coronary Angioplasty", The New England Journal of Medicine, Vol. 301, No. 2, pages 61-68, July 12, 1979, Gruntzig et al. disclose an improved technique for the use of a dilating catheter to relieve arterial stenosis. According to Gruntzig et al. the technique of transluminal angioplasty for the treatment of atherosclerotic obstruction of the femoral artery was first introduced in 1964 by Dotter and Judkins.
Balloon catheters are not limited in their use to the relief of arterial stenosis but have been found useful in many medical applications involving not only insertion into blood vessels but also involving insertion into a variety of body cavities.
Although medical procedures using balloon catheters are still in the exploratory stage, particularly in the United States, considerable art is already available on the use of balloon catheters and their fabrication. Representative of such art are U.S. Pat. Nos. 4,093,484; 4,154,244; and 4,254,774. Balloons can be made from a variety of known materials which are generally of the thermoplastic polymeric type. Included among the known materials disclosed in the aforesaid patents are ethylene-butylene-styrene block copolymers admixed with low molecular weight polystyrene and, optionally, polypropylene, and similar compositions employing butadiene or isoprene in place of the ethylene and butylene; poly(vinyl chloride); polyurethanes; copolyesters; thermoplastic rubbers; siliconepolycarbonate copolymers; and ethylene-vinyl acetate copolymers.
It is an object of this invention to provide balloons which exhibit physical properties, for example, toughness, flexibility and tensile strength, superior to those exhibited by balloons known in the art. A further object is to provide balloons which, because of their superior physical properties, have thinner wall thicknesses than commonly used balloons. Another object is to provide such balloons which, because of their flexibility and thin walls, are more readily collapsible and more easily transportable in the body. It is also an object of the invention to provide such balloons which exhibit very little elongation or creep radially, collectively referred to herein as radial expansion, when inflated to the pressure necessary to perform the desired medical procedure. A further object is to provide such balloons which, if they burst under pressure, burst in the axial direction to give an axial rupture, thus ensuring atraumatic removal, it being well known that a balloon which bursts in a circumferential direction may provide fragments which either are removable only with difficulty or are not removable at all nonsurgically. A further object is to provide such balloons which, because of their superior physical properties, can be used in medical procedures with a greater probability of success. Another object is to provide such balloons which, because of their superior physical properties, can be used in medical procedures under conditions not currently achievable using commonly available balloons. Still another object is to provide a process for fabricating such balloons. These and other objects will become apparent from the following discussion of the invention.